Disruption Of Membrane Integrity Research Articles

Synthesis, antifungal activity and mechanism of action of novel chalcone derivatives containing 1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazole.

A series of chalcone derivatives containing 1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazole was designed and synthesized. Structures of all compounds were characterized by 1H NMR, 13C NMR, 19F NMR, and HRMS. The biological activities of the compounds were determined with the mycelial growth rate method, and further studies showed that some compounds had good antifungal activities at the concentration of 100μg/mL. The EC50 value of compound L31 was 15.9μg/mL against Phomopsis sp., which were better than that of azoxystrobin (EC50 value was 69.4μg/mL). In addition, the mechanism of action of compound L31 shown that compound can affect mycelial growth by disrupting membrane integrity against Phomopsis sp., and that the higher the concentration of the compound is, the greater the disruption of membrane integrity is.

Enzymatic Self-Assembly of Adamantane-Peptide Conjugate for Combating Staphylococcus aureus Infection.

Staphylococcus aureus (S. aureus) remains a leading cause of bacterial infections. However, eradication of S. aureus infections with common antibiotics is increasingly difficult due to outbreaks of drug resistance. Therefore, new antibiotic classes and antibacterial strategies are urgently in demand. Herein, it is shown that an adamantane-peptide conjugate, upon dephosphorylation by alkaline phosphatase (ALP) constitutively expressed on S. aureus, generates fibrous assemblies in situ to combat S. aureus infection. By attaching adamantane to a phosphorylated tetrapeptide Nap-Phe-Phe-Lys-Tyr(H2 PO3 )-OH, the rationally designed adamantane-peptide conjugate Nap-Phe-Phe-Lys(Ada)-Tyr(H2 PO3 )-OH (Nap-FYp-Ada) is obtained. Upon bacterial ALP activation, Nap-FYp-Ada is dephosphorylated and self-assembles into nanofibers on the surface of S. aureus. As revealed by cell assays, the assemblies of adamantane-peptide conjugates interact with cell lipid membrane and thereby disrupt membrane integrity to kill S. aureus. Animal experiments further demonstrate the excellent potential of Nap-FYp-Ada in the treatment of S. aureus infection in vivo. This work provides an alternative approach to design antimicrobial agents.

Temporin-GHb-Derived Peptides Exhibit Potent Antibacterial and Antibiofilm Activities against Staphylococcus aureus In Vitro and Protect Mice from Acute Infectious Pneumonia.

With the continuous development of drug resistance in bacteria to traditional antibiotics, the demand for novel antibacterial agents is urgent. Antimicrobial peptides (AMPs) are promising candidates because of their unique mechanism of action and low tendency to induce drug resistance. Previously, we cloned temporin-GHb (hereafter referred to simply as "GHb") from Hylarana guentheri. In this study, a series of derived peptides were designed, namely, GHbR, GHbK, GHb3K, GHb11K, and GHbK4R. The five derived peptides had stronger antibacterial activities against Staphylococcus aureus than the parent peptide GHb and could effectively inhibit the formation of biofilms and eradicate mature biofilms in vitro. GHbR, GHbK, GHb3K, and GHbK4R exerted bactericidal effects by disrupting membrane integrity. However, GHb11K exhibited bacteriostatic efficacy with toroidal pore formation on the cell membrane. In comparison to GHbK4R, GHb3K showed much lower cytotoxicity against A549 alveolar epithelial cells, with an IC50 > 200 μM, which was much higher than its minimal inhibitory concentration (MIC = 3.1 μM) against S. aureus. The anti-infection potential of GHbK4R and GHb3K was investigated in vivo. Compared with vancomycin, the two peptides displayed significant efficacy in a mouse model of acute pneumonia infected with S. aureus. Both GHbK4R and GHb3K also had no obvious toxicity to normal mice after intraperitoneal administration (15 mg/kg) for 8 days. Our results indicate that GHb3K and GHbK4R might be promising candidates for the treatment of bacterial pneumonia infected with S. aureus.

Purification of PaTx-II from the Venom of the Australian King Brown Snake and Characterization of Its Antimicrobial and Wound Healing Activities.

Infections caused by multi-drug-resistant (MDR) bacteria are a global threat to human health. As venoms are the source of biochemically diverse bioactive proteins and peptides, we investigated the antimicrobial activity and murine skin infection model-based wound healing efficacy of a 13 kDa protein. The active component PaTx-II was isolated from the venom of Pseudechis australis (Australian King Brown or Mulga Snake). PaTx-II inhibited the growth of Gram-positive bacteria in vitro, with moderate potency (MICs of 25 µM) observed against S. aureus, E. aerogenes, and P. vulgaris. The antibiotic activity of PaTx-II was associated with the disruption of membrane integrity, pore formation, and lysis of bacterial cells, as evidenced by scanning and transmission microscopy. However, these effects were not observed with mammalian cells, and PaTx-II exhibited minimal cytotoxicity (CC50 > 1000 µM) toward skin/lung cells. Antimicrobial efficacy was then determined using a murine model of S. aureus skin infection. Topical application of PaTx-II (0.5 mg/kg) cleared S. aureus with concomitant increased vascularization and re-epithelialization, promoting wound healing. As small proteins and peptides can possess immunomodulatory effects to enhance microbial clearance, cytokines and collagen from the wound tissue samples were analyzed by immunoblots and immunoassays. The amounts of type I collagen in PaTx-II-treated sites were elevated compared to the vehicle controls, suggesting a potential role for collagen in facilitating the maturation of the dermal matrix during wound healing. Levels of the proinflammatory cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2) and interleukin-10 (IL-10), factors known to promote neovascularization, were substantially reduced by PaTx-II treatment. Further studies that characterize the contributions towards efficacy imparted by in vitro antimicrobial and immunomodulatory activity with PaTx-II are warranted.

Facile Synthesis of Magnetic Nigella Sativa Seeds: Advances on Nano-Formulation Approaches for Delivering Antioxidants and Their Antifungal Activity against Candida albicans

This article reports on incorporating magnetic nanoparticles into natural carbon frameworks derived from Nigella Sativa seeds and their synthesis via co-precipitation reactions for application in biomedicine. The magnetic Nigella Sativa Seeds (Magnetic NSS), a metal oxide-based bio-nanomaterial, has shown excellent water diaper presence due to the presence of a wide range of oxygenous hydroxyl and carboxyl groups. The physicochemical properties of the composites were characterized extensively using Fourier transform infrared spectroscopy (FTIR), powder-X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental analysis, transmission electron microscopy (TEM), and vibrating-sample magnetometer. Furthermore, synthesized magnetic NSS showed antioxidant and antifungal activity. The antifungal susceptibility was further tested against Candida albicans with a MIC value of 3.125 µg/mL. Analysis of antioxidant defense enzymes was determined quantitatively; the results suggested that antioxidant enzyme activity increase with increased magnetic NSS concentration. Furthermore, biofilm inhibition assay from scanning electron microscopy results revealed that magnetic NSS at the concentration of 3.5 μg/mL has anti-biofilm properties and can disrupt membrane integrity.

Role of the Peli1-RIPK1 Signaling Axis in Methamphetamine-Induced Neuroinflammation.

Severe neurological inflammation is one of the main symptoms of methamphetamine (meth)-induced brain injury. Studies have demonstrated that meth exposure facilitates neuroinflammation via Pellino E3 ubiquitin protein ligase 1 (Peli1)-mediated signaling. However, the involved mechanisms remain incompletely understood. Herein, we used Peli1-/- mice and Peli1-knockdown microglial BV2 cells to decipher the roles of Peli1 and downstream signaling in meth-induced neuroinflammation. After meth administration for seven consecutive days, Peli1-/- mice exhibited better learning and memory behavior and dramatically lower interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6 levels than wild-type mice. Moreover, in vitro experiments revealed that Peli1 knockdown significantly attenuated the meth-induced upregulation of cytokines. Besides, meth markedly activated and increased the levels of receptor-interacting protein kinase 1 (RIPK1), and Peli1 knockout or knockdown prevented these effects, indicating that RIPK1 participated in meth-induced Peli1-mediated inflammation. Specifically, treating the cells with necrostatin-1(Nec-1), an antagonist of RIPK1, remarkably inhibited the meth-induced increase in IL-1β, TNF-α, and IL-6 expression, confirming the involvement of RIPK1 in Peli1-mediated neuroinflammation. Finally, meth induced a dramatic transfer of the mixed lineage kinase domain-like protein, a downstream effector of RIRK1, to the cell membrane, disrupting membrane integrity and causing cytokine excretion. Therefore, targeting the Peli1-RIPK1 signaling axis is a potentially valid therapeutic approach against meth-induced neuroinflammation.

Beyond brewing: β-acid rich hop extract in the development of a multifunctional polylactic acid-based food packaging

Hops' (Humulus lupulus L.) phytochemicals are well known for their bioactivity. In the present study, the functional properties of hop extract rich in β-acids, as potassium-salts structures (KBA), were investigated to develop a sustainable active food packaging. Polylactic acid (PLA)-based sheets were incorporated with increasing concentrations of hop extract (0.1–5 % w/w in terms of KBA) and characterized through performance and bioactive properties. KBA-added sheets presented decreased crystallinity and affected mechanical and thermal properties, especially with higher KBA amounts. The sheets' surface hydrophobicity gradually decreased by KBA-extract addition, while the water vapor permeability was not affected. A Fickian diffuse behavior and a better fit to application in fatty foods were observed during release tests. UV-blocking and antioxidant properties were improved by KBA incorporation. Furthermore, results from antibacterial assays revealed great susceptibility of Staphylococcus aureus and Listeria monocytogenes towards sheets added with 5 % of KBA. Moreover, the atomic force microscopy (AFM) observations revealed that KBA led to strong effects on the cell membranes of both bacteria, including disruption of membrane integrity and cell death. Therefore, this study is a sign of great prospects of hop β-acids use, as KBA compound, in the production of sustainable active packaging for safe food shelf-life extension.

Cannabis sativa CBD Extract Exhibits Synergy with Broad-Spectrum Antibiotics against Salmonella enterica subsp. Enterica serovar typhimurium.

New generation antibiotics are needed to combat the development of resistance to antimicrobials. One of the most promising new classes of antibiotics is cannabidiol (CBD). It is a non-toxic and low-resistance chemical that can be used to treat bacterial infections. The antibacterial activity of Cannabis sativa L. byproducts, specifically CBD, has been of growing interest in the field of novel therapeutics. As research continues to define and characterize the antibacterial activity that CBD possesses against a wide variety of bacterial species, it is important to examine potential interactions between CBD and common therapeutics such as broad-spectrum antibiotics. In this study it is demonstrated that CBD-antibiotic (combination of CBD and antibiotic) co-therapy can effectively fight Salmonella typhimurium (S. typhimurium) via membrane integrity disruption. This research serves to examine the potential synergy between CBD and three broad-spectrum antibiotics (ampicillin, kanamycin, and polymyxin B) for potential CBD-antibiotic co-therapy. In this study, it is revealed that S. typhimurium growth is inhibited at very low dosages of CBD-antibiotic. This interesting finding demonstrates that CBD and CBD-antibiotic co-therapies are viable novel alternatives to combating S. typhimurium.

On-Chip Single-Cell Bioelectrical Analysis for Identification of Cell Electrical Phenotyping in Response to Sequential Electric Signal Modulation.

In recent years, an interesting biomarker called membrane breakdown voltage has been examined using artificial planar lipid bilayers. Even though they have great potential to identify cell electrical phenotyping for distinguishing similar cell lines or cells under different physiological conditions, the biomarker has not been evaluated in the context of living cell electrical phenotyping. Herein, we present a single-cell analysis platform to continuously measure the electric response in a large number of cells in parallel using electric frequency and voltage variables. Using this platform, we measured the direction of cell displacement and transparent cell image alteration as electric polarization of the cell responds to signal modulation, extracting the dielectrophoretic crossover frequency and membrane breakdown voltage for each cell, and utilizing the measurement results in the same spatiotemporal environment. We developed paired parameters using the dielectrophoretic crossover frequency and membrane breakdown voltage for each cell and evaluated the paired parameter efficiency concerning the identification of two different breast cancer cells and cell drug response. Moreover, we showed that the platform was able to identify cell electrical phenotyping, which was generated by subtle changes in cholesterol depletion-induced cell membrane integrity disruption when the paired parameter was used. Our platform introduced in this paper is extremely useful for facilitating more accurate and efficient evaluation of cell electrical phenotyping in a variety of applications, such as cell biology and drug discovery.

Garvicin Q: characterization of biosynthesis and mode of action

Bacteriocins are ribosomally synthesized antimicrobial peptides, that either kill target bacteria or inhibit their growth. Bacteriocins are used in food preservation and are of increasing interest as potential alternatives to conventional antibiotics. In the present study, we show that Lactococcus petauri B1726, a strain isolated from fermented balsam pear, produces a heat-stable and protease-sensitive compound. Following genome sequencing, a gene cluster for production of a class IId bacteriocin was identified consisting of garQ (encoding for the bacteriocin garvicin Q), garI (for a putative immunity protein), garC, and garD (putative transporter proteins). Growth conditions were optimized for increased bacteriocin activity in supernatants of L. petauri B1726 and purification and mass spectrometry identified the compound as garvicin Q. Further experiments suggest that garvicin Q adsorbs to biomass of various susceptible and insusceptible bacteria and support the hypothesis that garvicin Q requires a mannose-family phosphotransferase system (PTSMan) as receptor to kill target bacteria by disruption of membrane integrity. Heterologous expression of a synthetic garQICD operon was established in Corynebacterium glutamicum demonstrating that genes garQICD are responsible for biosynthesis and secretion of garvicin Q. Moreover, production of garvicin Q by the recombinant C. glutamicum strain was improved by using a defined medium yet product levels were still considerably lower than with the natural L. petauri B1726 producer strain.Collectively, our data identifies the genetic basis for production of the bacteriocin garvicin Q by L. petauri B1726 and provides insights into the receptor and mode of action of garvicin Q. Moreover, we successfully performed first attempts towards biotechnological production of this interesting bacteriocin using natural and heterologous hosts.

In Vitro Antimicrobial Effects and Inactivation Mechanisms of 5,8-Dihydroxy-1,4-Napthoquinone.

Naphthoquinones are an important class of natural organic compounds that have antimicrobial effects. However, the mechanisms of their action remain to be elucidated. Therefore, the antimicrobial activity of the chemically synthesized naphthoquinone derivative, 5,8-dihydroxy-1,4-naphthoquinone, was investigated in this study against 10 different microorganisms. Its inhibitory activity was evident against Bacillus cereus, Proteus vulgaris, Salmonella enteritidis, Staphylococcus epidermidis, S. aureus, and Candida albicans, and its MIC50 values were determined to be 14, 10, 6, 2, 4, 1.2, and <0.6 µg/mL, respectively. Moreover, the crystal violet uptake, TTC dehydrogenase activity, protein/DNA leakage, and DNA damage of the compound in these microorganisms were also investigated to reveal the antimicrobial mechanisms. In addition, scanning electron microscopy was used to detect physiological damage to the cell membrane of S. epidermidis, S. aureus, and C. albicans, which was most severe in the crystal violet uptake assay. The overall results showed that 5,8-dihydroxy-1,4-naphthoquinone exhibited its effects on S. aureus, S. epidermidis, and C. albicans by various mechanisms, especially membrane damage and membrane integrity disruption. It also caused DNA leakage and damage along with respiratory chain disruption (78%) in C. albicans. Similarly, it caused varying degrees of reduction in the respiratory activity of S. aureus (47%), S. epidermidis (16%), B. cereus (12%), S. enteritidis (9%), and P. vulgaris (8%). Therefore, 5,8-dihydroxy-1,4-naphthoquinone proved to be a very effective antifungal and antibacterial agent and could be considered a new potential drug candidate, inspiring further discoveries in these microorganisms.

Bactericidal Activity of Carvacrol against Streptococcus pyogenes Involves Alteration of Membrane Fluidity and Integrity through Interaction with Membrane Phospholipids

Background: Carvacrol, a mono-terpenoid phenol found in herbs, such as oregano and thyme, has excellent antibacterial properties against Streptococcus pyogenes. However, its mechanism of bactericidal activity on S. pyogenes has not been elucidated. Objectives: This study investigated the bactericidal mechanism of carvacrol using three strains of S. pyogenes. Methods: Flow cytometry (FCM) experiments were conducted to determine carvacrol’s membrane permeabilization and cytoplasmic membrane depolarization activities. Protoplasts of S. pyogenes were used to investigate carvacrol’s effects on the membrane, followed by gel electrophoresis. The carvacrol-treated protoplasts were examined by transmission electron microscopy (TEM) to observe ultrastructural morphological changes. The fluidity of the cell membrane was measured by steady-state fluorescence anisotropy. Thin-layer chromatographic (TLC) profiling was conducted to study the affinity of carvacrol for membrane phospholipids. Results: Increased membrane permeability and decreased membrane potential from FCM and electron microscopy observations revealed that carvacrol killed the bacteria primarily by disrupting membrane integrity, leading to whole-cell lysis. Ultra-structural morphological changes in the membrane induced by carvacrol over a short period were confirmed using the S. pyogenes protoplast and membrane isolate models in vitro. In addition, changes in the other biophysical properties of the bacterial membrane, including concentration- and time-dependent increased fluidity, were observed. TLC experiments showed that carvacrol preferentially interacts with membrane phosphatidylglycerol (P.G.), phosphatidylethanolamine (P.E.), and cardiolipins (CL). Conclusions: Carvacrol exhibited rapid bactericidal action against S. pyogenes by disrupting the bacterial membrane and increasing permeability, possibly due to affinity with specific membrane phospholipids, such as P.E., P.G., and CL. Therefore, the bactericidal concentration of carvacrol (250 µg/mL) could be used to develop safe and efficacious natural health products for managing streptococcal pharyngitis or therapeutic applications.

Investigation of morphological and biochemical changes of zinc oxide nanoparticles induced toxicity against multi drug resistance bacteria

BackgroundBiofilms are microbial colonies that remain enclosed in an organic polymeric matrix substance on biotic and abiotic surfaces, allowing them to colonize medical equipments and involved in most device associated life intimidating infections. Due to their antimicrobial resistance there is an urgent need to discover novel biofilm preventive and therapeutic agents. MethodsZnO NPs were synthesized using cyanobacteria Gleocapsa gelatinosa cell extract through green and cost-effective approach. Physiochemical characterization was done to determine their morphologies and size distribution. Antibiofilm and eradication activity of ZnO NPs was determined. Cell viability and internalization ability of ZnO NPs into biofilm was analyzed by flow cytometry. Confocal microscopy was done to visualize the disrupted biofilm morphology treated with ZnO NPs. ResultsIt was observed that ZnONPs were spherical in shape with 31–35 nm size and were moderately dispersed. ZnO NPs exhibited high antibiofilm activity against B. cereus and E. coli with minimum biofilm inhibitory concentration (MBIC) of ZnO NPs at 46.8 µg ml−1 and 93.7 µg ml−1. Flow cytometry analysis confirmed the reduced bacterial cell viability due to increased permeability, altered bacterial growth and enhanced production of intracellular ROS. Disruption of membrane integrity exhibited with reduced exopolysaccharides secretion and leakage of nucleic acids through UV–Vis spectroscopy. Results of confocal microscopy highlighted strong interaction of ZnO NPs with intracellular components leading to biofim destruction. ConclusionsThis study emphasizes the potential mechanisms underlying the selective bactericidal properties of ZnO NPs and highlighted the strong interaction of ZnO NPs with intracellular components leading to biofim destruction. Therefore, ZnO NPs could be considered as a promising antibiofilm agent and thus could expand the possibility to use as therapeutic agent.

A New Discovery towards Novel Skeleton of Benzimidazole‐Conjugated Pyrimidinones as Unique Effective Antibacterial Agents

Comprehensive SummaryA class of new potential antibacterial agents with distinctive pyrimidinone benzimidazole skeleton was developed through nucleophilic substitution and Biginelli reaction starting from urea, ethyl 4‐chloroacetoacetate and various aldehydes. Some target molecules exhibited strong antibacterial activities, especially pyrimidinone benzimidazole hybrid 9e possessed the strongest inhibitory effects on the growth of E. faecalis and P. aeruginosa with a lower MIC value of 1 μg/mL than norfloxacin. Moreover, compound 9e displayed strong antibiofilm capacity, low drug resistance and excellent biosafety toward human red blood cells. Further research revealed that compound 9e could disrupt membrane integrity and cause leakage of cellular components such as proteins and nucleic acids. Meanwhile, compound 9e could decrease lactate dehydrogenase activity, block cell metabolism and interact with DNA in an intercalation manner. ADMET analysis predicated that molecule 9e possessed promising pharmacokinetic properties and good bioavailability profile.

Human β defensins-1, an antimicrobial peptide, kills Candida glabrata by generating oxidative stress and arresting the cell cycle in G0/G1 phase

Candida glabrata is the most frequently isolated non-albicans Candida species in clinical samples and is known to develop resistance to commonly used antifungal drugs. Human β defensins (hBDs) are antimicrobial peptides of immune systems and are active against a broad range of pathogens including Candida species. Herein, the antifungal effect of hBD-1 and its mechanism of action in C. glabrata was studied. The antifungal susceptibility of hBD-1 against C. glabrata was calculated by broth microdilution assay. To study the mechanism of antifungal action, the impact of hBD-1 on cell cycle, expression of oxidative stress enzymes, and membrane disintegration were assessed. The susceptibility results confirmed that hBD-1 possessed the minimum inhibitory concentration of 3.12 µg/mL and prevented the growth and caused yeast cell death to various extents. The peptide at subinhibitory and inhibitory concentrations blocked the cell cycle in C. glabrata in G0/G1 phase and disturbed the activity of primary and secondary antioxidant enzymes. Furthermore, at higher concentrations disruption of membrane integrity was observed. Altogether, hBD-1 showed candidicidal activity against C. glabrata and was able to induce oxidative stress and arrested cell cycle in C. auris and therefore has a potential to be developed as an antifungal drug against C. glabrata.

Effects of Selected Metal Nanoparticles (Ag, ZnO, TiO2) on the Structure and Function of Reproductive Organs.

Various studies have shown that the reproductive organs are highly sensitive to toxic elements found in the environment. Due to technological progress, the use of nanoparticles has become more common nowadays. Nanoparticles are used for drug delivery because their dimensions allow them to circulate throughout the body and enter directly into the cell. Antimicrobial properties are increasingly used in the manufacture of medical devices, textiles, food packaging, cosmetics, and other consumer products. Nanoparticles provide several benefits, but aspects related to their effects on living organisms and the environment are not well known. This review summarizes current in vivo, and in vitro animal studies focused on the evaluation of toxicity of selected metal nanoparticles (Ag, ZnO, TiO2) on male and female reproductive health. It can be concluded that higher concentrations of metal nanoparticles in the male reproductive system can cause a decrease in spermatozoa motility, viability and disruption of membrane integrity. Histopathological changes of the testicular epithelium, infiltration of inflammatory cells in the epididymis, and prostatic hyperplasia have been observed. Nanoparticles in the female reproductive system caused their accumulation in the ovaries and uterus. Metal nanoparticles most likely induce polycystic ovary syndrome and follicular atresia, inflammation, apoptosis, and necrosis also occurred.

Combination Effect of Novel Bimetallic Ag-Ni Nanoparticles with Fluconazole against Candida albicans

The increasing frequency of antifungal drug resistance among pathogenic yeast “Candida” has posed an immense global threat to the public healthcare sector. The most notable species of Candida causing most fungal infections is Candida albicans. Furthermore, recent research has revealed that transition and noble metal combinations can have synergistic antimicrobial effects. Therefore, a one-pot seedless biogenic synthesis of Ag-Ni bimetallic nanoparticles (Ag-Ni NPs) using Salvia officinalis aqueous leaf extract is described. Various techniques, such as UV–vis, FTIR, XRD, SEM, EDX, and TGA, were used to validate the production of Ag-Ni NPs. The antifungal susceptibility of Ag-Ni NPs alone and in combination with fluconazole (FLZ) was tested against FLZ-resistant C. albicans isolate. Furthermore, the impacts of these NPs on membrane integrity, drug efflux pumps, and biofilms formation were evaluated. The MIC (1.56 μg/mL) and MFC (3.12 μg/mL) results indicated potent antifungal activity of Ag-Ni NPs against FLZ-resistant C. albicans. Upon combination, synergistic interaction was observed between Ag-Ni NPs and FLZ against C. albicans 5112 with a fractional inhibitory concentration index (FICI) value of 0.31. In-depth studies revealed that Ag-Ni NPs at higher concentrations (3.12 μg/mL) have anti-biofilm properties and disrupt membrane integrity, as demonstrated by scanning electron microscopy results. In comparison, morphological transition was halted at lower concentrations (0.78 μg/mL). From the results of efflux pump assay using rhodamine 6G (R6G), it was evident that Ag-Ni NPs blocks the efflux pumps in the FLZ-resistant C. albicans 5112. Targeting biofilms and efflux pumps using novel drugs will be an alternate approach for combatting the threat of multi-drug resistant (MDR) stains of C. albicans. Therefore, this study supports the usage of Ag-Ni NPs to avert infections caused by drug resistant strains of C. albicans.

Cinnamomum: The New Therapeutic Agents for Inhibition of Bacterial and Fungal Biofilm-Associated Infection.

Due to the potent antibacterial properties of Cinnamomum and its derivatives, particularly cinnamaldehyde, recent studies have used these compounds to inhibit the growth of the most prevalent bacterial and fungal biofilms. By inhibiting flagella protein synthesis and swarming motility, Cinnamomum could suppress bacterial attachment, colonization, and biofilm formation in an early stage. Furthermore, by downregulation of Cyclic di‐guanosine monophosphate (c‐di‐GMP), biofilm-related genes, and quorum sensing, this compound suppresses intercellular adherence and accumulation of bacterial cells in biofilm and inhibits important bacterial virulence factors. In addition, Cinnamomum could lead to preformed biofilm elimination by enhancing membrane permeability and the disruption of membrane integrity. Moreover, this substance suppresses the Candida species adherence to the oral epithelial cells, leading to the cell wall deformities, damage, and leakages of intracellular material that may contribute to the established Candida’s biofilm elimination. Therefore, by inhibiting biofilm maturation and destroying the external structure of biofilm, Cinnamomum could boost antibiotic treatment success in combination therapy. However, Cinnamomum has several disadvantages, such as poor solubility in aqueous solution, instability, and volatility; thus, the use of different drug-delivery systems may resolve these limitations and should be further considered in future investigations. Overall, Cinnamomum could be a promising agent for inhibiting microbial biofilm-associated infection and could be used as a catheter and other medical materials surface coatings to suppress biofilm formation. Nonetheless, further in vitro toxicology analysis and animal experiments are required to confirm the reported molecular antibiofilm effect of Cinnamomum and its derivative components against microbial biofilm.

Evaluation of antibacterial and antifungal properties of Lonicera japonica Thunb . Leaves mediated silver nanoparticles and mechanism investigation

Lonicera japonica Thunb. leaves were used to biosynthesize silver nanoparticles (AgNPs), while its antibacterial and antifungal properties were investigated. Reaction conditions of AgNPs which characterized were optimized. The maximum absorption wavelength of the AgNPs was located about 400 nm, with a spherical shape and a particle size of 14.87±4.07 nm. Produced AgNPs showed effective antibacterial activities against tested bacterial strains. Minimal inhibitory concentrations and minimum bactericidal concentrations of the AgNPs were 0.25 and 0.5 mg/mL for Escherichia coli (E. coli), and 0.5 and 1.0 mg/mL for Staphylococcus aureus, respectively. According to the mechanism study, AgNPs generated morphological changes in E. coli and disrupted membrane integrity. Furthermore, AgNPs which showed effective dose-dependent inhibitory effects against Penicillium citrinum could suppress the growth of fungal mycelium on citrus peels. Conclusively, AgNPs generated by this facile and green method showed effective antimicrobial activity, which is promising in food processing and preservation.

Therapeutic potential for amyloid surface inhibitor: only amyloid-β oligomers formed by secondary nucleation disrupt lipid membrane integrity.

Inhibition of amyloid-β peptide (Aβ) aggregation is a promising therapeutic strategy for Alzheimer's disease (AD), as Aβ aggregation is generally believed to trigger AD pathology. Pre-fibril Aβ-oligomers induce membrane disruption and are crucial to neurotoxicity. We have previously designed a short peptide called cyclic helical amyloid surface inhibitor (cHASI) that can selectively bind to the Aβ fibril surface. Here, we use cHASI to efficiently inhibit the surface-catalysed secondary nucleation process of Aβ in a lipid membrane environment. By incubating Aβ monomers with lipid vesicles, we show that during the assembly of Aβ into amyloid fibrils, oligomers are formed that markedly disrupt the lipid bilayer. Remarkably, when Aβ monomers are incubated with cHASI, although Aβ forms amyloid fibrils via primary nucleation and elongation, this pathway to fibrils does not damage the lipid bilayer. This indicates that only oligomers produced during secondary surface nucleation disrupt membrane integrity. The protective effect of cHASI is confirmed by cytotoxicity assays. Our study highlights the therapeutic potential for inhibiting the secondary nucleation process in Aβ aggregation, rather than inhibiting all pathways to fibril formation.